Paper towel

ABSTRACT

The present invention relates to a paper towel that can be provided with dry crepes with no need for involving a large equipment investment. The paper towel contains one or more of chemical pulp, mechanical pulp, de-inked pulp, and recycled pulp, being provided with crepes in an off-machine process by use of a microcreper, such as a MICREX®/Microcreper™ system, and having a basis weight of 32.2 to 64.3 gsm, a density of 0.130 to 0.150 g/cm 3 , which is obtained by dividing the basis weight by the caliper (μm), and the number of crepes (cpi) of 12 to 30.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a paper towel, and more particularly relates to a paper towel that can be provided with dry crepes with no need for involving a large equipment investment. In addition, the present invention relates to a rolled paper towel, having a moderate stiffness, softness, and water absorbency, and being suitable for “Away From home”, in commercial and industrial settings such as office and government buildings, hotels, schools, airports, amusement parks, hospitals, highway rest stops—anywhere restroom and kitchen facilities are not in a private home.

Description of the Related Art

In U.S. Pat. No. 7,449,085B2, there are disclosed absorptive paper products, such as paper towels, having a combination of a high absorbent capacity and a moderate to low rate of absorbency for hand protection. More particularly, there is disclosed a low-density paper product having one or more plies essentially composed of hardwood kraft pulp, softwood kraft pulp, or blends thereof, and having a discontinuous moisture retardant coating on the surface thereof.

In Example 3 given in the 14th to 15th columns in the same U.S. Pat. No. 7,449,085B2 patent document, there is disclosed a paper towel that has a basis weight of 58.4 grams per square meter (gsm) and a crepe ratio of 20%, being produced by use of an MICREX®/Microcreper system, which is manufactured by Micrex Corporation. The density of the paper product (as measured by Bulk values) is defined to be preferably 10 cubic centimeters or greater per gram (under 0.10 g/cm³).

U.S. Pat. No. 7,449,085B2 also disclosed a nonwoven fabric that is provided with crepes by use of an MICREX®/Microcreper system. The paper towels disclosed in U.S. Pat. No. 7,449,085B2 are composed mainly of a virgin pulp, thereby being inevitably expensive.

Citation of any document herein is not intended as an admission that such document is pertinent prior art, or considered material to the patentability of any claim of the present application. Any statement as to content or a date of any document is based on the information available to applicant at the time of filing and does not constitute an admission as to the correctness of such a statement.

SUMMARY OF THE INVENTION

In view of the problem of the paper towel in US74490985 being expensive, the present invention has been made to provide a paper towel that is not only inexpensive but also has a high productivity, containing inexpensive recycled pulp, especially de-inked pulp, OCC (Old Corrugated Container) pulp, or the like, and that can be adjusted for hue through appropriate adjustment of the contents of chemical pulp, mechanical pulp, de-inked pulp, and recycled pulp.

In addition, the present invention provides a paper towel for which the original fabric for crepe processing can be conveniently obtained with no need for involving a large equipment investment, and thus the paper towel can be efficiently and inexpensively manufactured, being provided with a moderate stiffness, softness, and water absorbency.

As a result of an intensive study to solve the above problem, the inventors of the present invention have conceived an idea of using inexpensive de-inked pulp or recycled pulp, while performing off-line crepe processing to provide an original fabric with a moderate stiffness, softness, and water absorbency, and thus have completed the present invention.

In other words, the present invention provides a paper towel that contains one or more of chemical pulp, mechanical pulp, de-inked pulp, and recycled pulp, being provided with crepes in an off-machine process, such as by use of an MICREX®/Microcreper™ system, and having a basis weight of 32.2 to 64.3 gsm, a density of 0.130 to 0.150 g/cm³, which is the basis weight divided by the caliper (μm), and the number of crepes (cpi; crepes per inch) of 12 to 30.

In one embodiment, the longitudinal stiffness is 170 to 240 mN·m, and the water absorbency is 250 to 420 sec/100 μL.

The present invention is as described above, and since it provides an elongation for an original fabric in off-line crepe processing, there is no need for involving a large equipment investment, and thus a creped product can be conveniently obtained, whereby the present invention offers the advantage that a paper towel having a moderate stiffness, softness, and water absorbency can be obtained efficiently at a low cost.

DETAILED DESCRIPTION OF THE INVENTION

A paper towel in accordance with the present invention contains one or more of chemical pulp, mechanical pulp, de-inked pulp, and recycled pulp, being provided with crepes, such as in an off-machine process by use of an MICREX®/Microcreper™ system, and having a basis weight of 32.2 to 64.3 gsm, a density of 0.130 to 0.150 g/cm³, which is obtained by dividing the basis weight by the caliper (μm), and the number of crepes (cpi) of 12 to 30. In addition, the paper towel has a longitudinal stiffness of 170 to 240 mN·m, and a water absorbency of 250 to 420 sec/100 μL.

In this way, by containing inexpensive de-inked pulp or recycled pulp, a paper towel that is inexpensive and has a high productivity can be obtained. In addition, by appropriately adjusting the contents of chemical pulp, mechanical pulp, and recycled pulp, adjustment of the hue of the paper towel can be achieved.

As the pulp for the paper towel, a well-known pulp can be used, and specifically, as the chemical pulp, NBKP, NUKP, LBKP, LUKP, NBSP, NUSP, LBSP, LUSP, and the like can be used. As the mechanical pulp, GP, TMP, CTMP, and the like can be used. As the recycled pulp, waste paper pulps, such as de-inked pulp, OCC (Old Corrugated Container) pulp, and NCC (New Corrugated Container) pulp, can be used.

By providing crepes to the paper towel in an off-machine process by use of an MICREX®/Microcreper™ system to give a specific number of crepes (cpi), a paper towel having a moderate softness and stiffness can be obtained. Further, there is no need for a large equipment investment, and a compact facility can be used for producing the present invention. In addition, the adhesive to be applied to the dryer cylinder, the release agent, and the doctor blade, which are used at the time of off-machine creping, can be conveniently managed. In particular, the MICREX®/Microcreper™ system, which is manufactured by Micrex Corporation, has a width of 1,067 to 3,150 mm and is compact (and thus effective for implementing the present invention) is a preferred off-machine process for producing crepes on a paper towel.

The microcreping process employed is preferably the microcreping process commercially available from the Micrex Corporation, Walpole, Mass. 02081, referred to as MICREX®/Microcreper™, but is not limited thereto, as other suitable microcreping process and system may be used. In the microcreping process, using a microcreper such as the MICREX®/Microcreper™ system, a pressure plate applies a predetermined amount of pressure extending across the path of a continuously supplied planar sheet of paper. The sheet is carried by a rotating drive roll on which the pressure is imparted through the sheet and against the rotating drive roll. The rotating drive roll has either a grooved surface or a flat (non-grooved) surface. While the sheet is under applied pressure, it then further impinges upon a flat retarding surface. The sheet is directed to the space between the retarding surface and a creping blade positioned in the path of the sheet. The creping blade is flat when the drive roll surface is flat. The creping blade is combed when the drive roll surface is grooved. The retarding surface in combination with the applied pressure induces the sheet into a creped form, with a resulting distortion of the planar aspect of the original sheet.

By specifying the basis weight to be within the above range of 32.2 to 64.3 gsm, a paper towel that is excellent in strength and productivity can be obtained. In addition, by specifying the density to be within the above range of 0.13 to 0.150 g/cm³, a paper towel that has the properties of moderate softness and stiffness can be obtained.

As stated above, the number of crepes (cpi) of the paper towel in accordance with the present invention is specified to be in the range of 12 to 30. By specifying the number of crepes (cpi) to be within this range, a paper towel having a moderate softness and stiffness can be obtained. In addition, by specifying the number of crepes (cpi) to be 12 to 30, the surface area is increased along with water absorption efficiency, and the dirt and dust that are picked up between crepes thereby provides improved dirt and dust removal performance when the paper towel of the present invention is used for cleaning by wiping off. In addition, the range of the number of crepes (cpi) being 12 to 30 also provides a moderate stiff feel, so that the paper towel of the present invention is suitable as a rolled paper towel for use in lavatories and the like in public facilities, such as sports grounds and movie houses.

The paper towel in accordance with the present invention has a longitudinal stiffness of 170 to 240 mN·m and a water absorbency of 250 to 420 sec/100 μL. In the case where the longitudinal stiffness and the water absorbency are in these ranges, a paper towel having a moderate stiffness and a moderate water absorbency can be achieved.

The number of crepes (cpi), which is defined as the number of irregularities per inch, is effective for use as an index of touch feel and water absorbency. The number of crepes (cpi) is preferably 12 or over, and it is particularly preferable to be in the range of 20 to 25. If the number of crepes (cpi) is under 12, the paper towel after processing is hard and inferior in touch feel, with the speed of water absorption speed being slow, resulting in a paper towel that is functionally insufficient. On the other hand, if the number of crepes (cpi) is over 12, a soft paper towel is provided that is both good in touch feel and water absorption speed.

It is preferable that the longitudinal stiffness be 170 to 240 mN·m. In the case where the longitudinal stiffness is in this range, a moderate stiffness as a paper towel for use in lavatories in public facilities, for example, can be obtained. In addition, it is preferable that the water absorbency of a paper towel for use in towel applications be under the range of 250 to 420 sec/100 μL.

Although the off-line crepe processing allows various elongations to be provided, it is most suitable to provide an elongation of 5 to 10% as that in the direction of MD. In the case where the elongation is in this range, there is no problem in small roll processing and emboss processing. If the elongation is under 5%, such an insufficient elongation causes a hole to be produced in the emboss processing, resulting in paper breakage, or pores to be produced, thereby causing a problem with operation and quality. On the other hand, if the elongation exceeds 10%, the tension at the time of small roll processing with a converter after, for example, the emboss processing of a creped paper is not stable, thereby causing a problem, such as an unsatisfactory roll figure of the small roll.

The paper towel in accordance with the present invention can be produced with all types of paper making machines, including well-known Fourdrinier machines, twin-wire paper machines (include gap former, hybrid former), cylinder paper machines, and Yankee paper machines. In addition, the paper towel in accordance with the present invention is produced mainly by single-layer paper making; however, it can also be produced by multiple layer paper making. In addition, a wet strength agent or a rosin size agent, such as a polyamide epichlorohydrin agent, can be added to the above-mentioned pulp slurry as a raw material as needed for paper making.

By selecting the pulp formulation, the hue can be adjusted to what is desired by a particular customer. Examples of pulp formulation are provided as follows: For brown 1, NUKP of 5%, RGP of 25 to 35%, and OCC of 60 to 70%; for brown 2, NUKP of 5 to 10%, RGP of 30 to 40%, and OCC of 50 to 65%; and for natural color, NBKP of 5 to 10%, RGP of 30 to 60%, and DIP of 30 to 60%.

Having now generally described the invention, the same will be more readily understood through reference to the following example which is provided by way of illustration and is not intended to be limiting of the present invention.

Example

Creped paper towels that were obtained by using an MICREX®/Microcreper™ system (having a width of 3,150 mm) from the original fabric for crepe processing that was produced by a twin-wire paper machine were evaluated. As a processing condition for the MICREX®/Microcreper™ system, by specifying a uniform microcreping speed of 140 mm/min (450 fpm), and varying the compaction ratio expressed as percentage (which is the difference in paper drawing speed between the Microcreper and the winder that is expressed as %), Examples 1 to 3 and Controls 1 to 3 were prepared. Control 1 did not meet the specifications for density, which is basis weight divided by caliper (μm), longitudinal stiffness, and crepe number of the present invention; Control 2 did not meet the specification for the above-described density of the present invention; and Control 3 did not meet the specifications for the above-described density and crepe number of the present invention.

Test and Evaluation Methods

The test and evaluation methods are presented in Table 1. As can be seen from the results in Table 1 below, Examples 1 to 3, which meet all the specifications of the paper towel of the present invention, were evaluated to be good or excellent on all the points of converting, softness, and water absorbency. Caliper is measured by the thickness micrometer of B.C.Ames Inc. “Model number: 2W”

Having now fully described this invention, it will be appreciated by those skilled in the art that the same can be performed within a wide range of equivalent parameters, concentrations, and conditions without departing from the spirit and scope of the invention and without undue experimentation.

While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications. This application is intended to cover any variations, uses, or adaptations of the inventions following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth as follows in the scope of the appended claims.

All references cited herein, including journal articles or abstracts, published or corresponding U.S. or foreign patent applications, issued U.S. or foreign patents, or any other references, are entirely incorporated by reference herein, including all data, tables, figures, and text presented in the cited references. Additionally, the entire contents of the references cited within the references cited herein are also entirely incorporated by references.

Reference to known method steps, conventional methods steps, known methods or conventional methods is not in any way an admission that any aspect, description or embodiment of the present invention is disclosed, taught or suggested in the relevant art.

The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art (including the contents of the references cited herein), readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance presented herein, in combination with the knowledge of one of ordinary skill in the art.

TABLE 1 density (basis Evaluation of effect Basis weight/ MD Water Number (sensory evaluation) Microcreper weight Caliper caliper) stiffness absorbency of crepes Water condition gsm μm g/cm³ mN · m sec/100 μL cpi Converting Stiffness absorbency Example 1 5.0 37.4 244 0.153 224 387 21 Good Excellent Good Example 2 5.2 35.2 267 0.132 179 293 18 Good Good Excellent Example 3 6.2 37.0 263 0.141 197 267 23 Good Excellent Excellent Control 1 3.1 35.1 324 0.108 291 576  9 No good No good No good Control 2 8.4 38.0 336 0.113 199 481 18 No good Good Good Control 3 3.7 33.9 378 0.090 204 912 10 No good No good No good Evaluation ISO536: Measured ISO534: ISO2493- Water Original Ease of Touch Water method 2012 by the 2011 2: absorption creping feeling absorbency thickness 2011 time when and when water micrometer water drop sharpness drop of of 100 μL of crepes; of 100 μL B.C.Ames is dropped total is dropped Inc. evaluation “Model number: 2 W” 

What is claimed is:
 1. A paper towel, comprising one or more of chemical pulp, mechanical pulp, and recycled pulp, and provided with crepes imparted by a microcreper in an off-machine process, the paper towel having a basis weight of 32.2 to 64.3 gsm, a density, which is the basis weight divided by the caliper (μm), of 0.130 to 0.150 g/cm³, and the number of crepes (cpi) of 12 to
 30. 2. The paper towel according to claim 1, having a longitudinal stiffness of 170 to 240 mN·m, and a water absorption of 250 to 420 sec/100 μL.
 3. The paper towel according to claim 1, wherein the off-machine process for providing crepes is by use of a MICREX®/Microcreper™ system. 